A suspected black water event has left up to 4000 fish dead in the Parramatta River.

The deaths occur due to a surge of de-oxygenated “black water” suffocating the fish.

EPA Director of Regulatory Operations James Goodwin told Deborah Knight they’re investigating the “distressing” deaths.

“This, most likely, has been a result of high-intensity storms that have washed organic matter into the waterway.”

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